The present invention relates to a focus detecting and indicating device for a camera which electrically indicates not only front focus, rear focus and correct focus but also the direction in which the photographing lens should be extended for correct focus.
A variety of methods have been proposed utilizing the principle in which the image of an object to be photographed is divided into two parts and in which the two parts coincide with each other when the photographing lens is correctly focused on the object hereinafter referred to as "focalization" when applicable. Furthermore, a variety of devices in which photoelectric conversion elements are disposed before and after a position equivalent to the position of the surface of a film in order to detect front focus, rear focus and correct focus have been provided in the art.
An automatic focus detecting device has been provided as a focus detecting mechanism in which the photographing lens is moved to the position of focalization by an electric motor. In addition, recently a focus detecting and indicating device has been proposed in which the photographing lens is moved manually instead of with a motor with the focus detecting condition being indicated electrically.
The latter manual device is advantageous in the following points. Unlike the former completely automatic device, the latter device does not need a drive circuit such as an electric motor and therefore the assembled device is smaller in size, lighter in weight and simpler in construction. In addition, with the latter device, it is determined by the photographer himself whether the photographing lens is focused on an object. Accordingly, drawbacks attributed to exclusive use of the automatic operation in the automatic focus detecting device are eliminated as a result of which a camera having a great degree of freedom is provided. Furthermore, is goes without saying that focalization can be sensed more readily than with an optical focus detecting technique because focalization detection is indicated by analog or digital data.
However, a focus detecting and indicating device which displays focalization only when the photographing lens is focused on the object suffers from a problem in that the photographer cannot determine in what direction the photographing lens should be moved in order for the lens to be focused on the object. Thus, the device is still inconvenient.
Accordingly, an object of this invention is to provide a focus detecting and indicating device for a camera in which it is determined and indicated whether or not the photographer is moving the photographing lens in the correct direction while front focus and rear focus are also indicated.